For wireless data communications between personal computers (PCs), mobile information terminals, PC peripheral devices and other devices located relatively close to each other, a standard of infrared data communication called the IrDA (Infrared Data Association) in general is known from, for example, Non-Patent Document 1. The IrDA standard defines a protocol for one-to-one device communications using a near infrared ray of light having a relatively high directivity (about +15 degrees). Basically, users need to adjust the position and orientation of their devices so that the two devices directly face each other for communication. Its communication speed in practical use is 4 Mbps. A newer version of the standard, called the IrBusrt, is being developed to achieve a higher speed of 100 Mbps.
In recent years, in addition to PCs and mobile information terminals, there are an increasing number of devices that can handle digital image data and/or digital audio data, with an increasing necessity for data transfer between such devices. The aforementioned infrared data communication eliminates the troublesome work of connecting cables for data transfer and is a good technique to produce a simple, low-cost system that can be used under the conditions in which the communicating devices are visible from each other at relatively short distances. Accordingly, most of the mobile phones and similar devices that have rapidly developed in recent years have the infrared communication function, which enables users to exchange phone numbers and other kinds of data between mobile phones. Moreover, some mobile phones function as a digital camera, a digital audio player, a GPS (global positioning system) terminal and other devices. Since such mobile phones can handle image/audio data, it is highly probable that the user retrieves image/audio data from PCs into his or her phone. Inversely, the user may capture images with the camera of the mobile phone and transfer the image data to a PC.
However, when, for example, a mobile phone is used for data communication with another device in the above-described conventional infrared data communication, it is not always easy to operate the phone. Since the directivity of the light used in the above-described data communication is relatively high, the user needs to manually adjust the orientation of the mobile phone so that the light emitted from the phone is correctly cast onto the target device (e.g. a PC). However, this adjusting work is not always easy because the user needs to rely solely on his or her senses to check the position of the target device and determine whether the target device is within a range in which the optical communication is performable. If at least one of the devices concerned is a mobile phone or similar device to be held by hand for operation, the device easily changes its position with the lapse of time due to hand movement, so that it is difficult to continuously maintain the communication in stable condition. If there is more than one device capable of optical communication within the communication range, the conventional techniques do not allow the user to select one of the devices as the target of the communication.
In recent years, a new type of system called the identification (ID) recognition camera system (or ID cam) has been proposed. It includes an optical beacon for emitting a blinking signal containing ID information and other items of information and a camera with a high-speed image sensor. For example, a system disclosed in Patent Document 1 captures a series of images captured with an ID recognition camera and outputs them as the scene image. Then, it decodes the blinking data of the optical beacon at maximum pixels to create an ID image. Practical applications of this ID recognition camera have been also proposed, such as an audio assist system disclosed in Patent Document 2 and an automatic photography system disclosed in Patent Document 3.
The above-described ID recognition camera system has the function of displaying an image captured with the camera, on which the ID information of each of the optical beacons detected within the captured image is shown at or near the detection point of each optical beacon, allowing users to select one or more of the optical beacons and using the related information. Such a system enables users to select one of the remote communication nodes and perform data communications with the selected communication node, using a information terminal to be held by hand.
[Patent Document 1] Unexamined Japanese Patent Publication No. 2003-323239
[Patent Document 2] Unexamined Japanese Patent Publication No. 2003-345376
[Patent Document 3] Unexamined Japanese Patent Publication No. 2003-348390
[Non-Patent Document 1] “About IrDA”, Special Interest Groups or SIGs, [Online], Infrared Data Association, [Searched on Jul. 2, 2004], Internet <URL: http://www.irda.org/displaycommon.cfm?an=1>